Many items and films are often bonded to a substrate or surface using an adhesive. Examples of these items include appliqués, stickers, and tape. Many of these items are meant to be affixed only temporarily to the substrate. The adhesives are often so formulated as to be a temporary adhesive so that the item adhered to the surface can be easily removed in the future. Many times these adhesives, however, become tenacious or hard to remove. With time and exposure to different elements, the once weak adhesive may become tenacious and not allow the removal of the item. Also, once a difficult adhesive is removed, residue is left behind. This must also be removed before a new adhesive film is applied. Therefore, the temporary item becomes essentially permanently secured to supporting surface. In addition, the adhesive often becomes nearly impervious to solvents at this point. On the other hand, weak adhesives may not be strong enough to secure an item for the temporary period desired. Therefore, after only a short time, and before it is desired to remove the item, the item may no longer be adhered to its support surface. Additional edge sealants and the like are sometimes added to prevent premature separation initiating from the edge.
Often the environment which the item is exposed to, after being affixed to a support surface, affects the longevity of the adhesive. In particular, ultra-violet (UV) exposure or other atmospheric conditions may increase the tenacity of the adhesive such that it is no longer easy to remove the item from the supporting surface. Atmospheric or other conditions, to which the adhesive is subjected, may conversely decrease the longevity of the adhesive such that it no longer holds the item in place as desired.
Oftentimes, appliqués are designed to allow for a clean removal by removing the appliqué as one piece. Appliqués for large applications, however, such as markings or decorations on aircraft, are extremely large. Therefore, there is a large surface area which may suffer damage during the time which the appliqué is applied to the surface. This, in turn, reduces the ability to remove the appliqué as one piece, thereby reducing the possibility of a clean removal of the appliqué from the surface.
Additional or supplementary adhesives are often used to hold films in place, in addition to the main adhesive layer. For example, an edge sealant may be applied to the front surface of a film to ensure that the edge does not become loosened over a period of time, even though the majority of the adhesive on the back of the film may still remain in place. Furthermore, these edge treatments or adhesives are commonly used because of the designed lack of strength of the main or primary adhesive to hold the film, due to the need to be able to remove the film in the future.
Therefore, it is desired to provide an adhesive which will allow for easy removal of a film at a desired time. The adhesives will also be cleanly and substantially completely removed from the surface with the film. It is desired that this adhesive be particularly strong so that other treatments, such as edge treatments or sealants, need not be used because the adhesive on the film itself is strong enough to hold the film in place. Furthermore, it is desired that the adhesive be strong enough to allow for generally impervious adhesion of the film to the substrate regardless of the conditions to which the film is exposed. Nevertheless, the film still needs to be readily removable when desired, and only when desired. Therefore, it is desired that the adhesive includes not only the strength and longevity of very strong adhesives, but also includes the ability to be removed easily without resorting to special chemicals.